Early childhood programs - interventions for children and their families occurring between the prenatal period and age 5 -- have expanded rapidly in the past several decades and represent substantial public investments in children's healthy development. Despite the hundreds of evaluation studies that have been conducted, we lack a comprehensive understanding of the effectiveness of different types of programs for improving children's wellbeing, and how program intensity matters within and across program types. Meta-analysis provides a systematic method for quantitative synthesis of the entire population of early childhood program evaluations and for the full range of children served by these programs. Yet to date, no meta-analysis has integrated multiple program types and programmatic components. As a result, policymakers and program administrators are unable to make evidence-based decisions about which types of programs or program components would be most effective for meeting their goals. We propose to: 1) complete the coding of a database of all rigorous early childhood program evaluations conducted between 1960 and 2007 in the United States; 2) perform a database-wide descriptive analysis of impacts on children's wellbeing by program type (early childhood education; parenting support; parent socioeconomic support; support of child nutrition) and key program characteristics; 3) understand how programmatic components and combinations of programmatic components predict the magnitude of effects in particular child domains; and 4) prepare and release the meta-analytic database for public use. One key innovation of our proposed project is that the database will be the first to encompass both parent- and child-focused programs. A second is that our inclusion criteria for evaluation studies are both broader (including, for example, econometric studies) and more rigorous than have been employed in prior meta-analyses in this area. Finally, ours will be the first meta- analytic database in early childhood to be prepared and released for public use.